This invention is related to an apparatus that is capable of delivering an accurate quantity of fluids to a process vessel or process system.
In many formulation applications, small amounts of fluids must be added during the manufacturing process. For example, in custom making of paint, an unpigmented resin solution or dispersion is blended with one or more mill bases which contain dispersed pigments, a liquid carrier and a dispersing resin. To achieve a color match of the paint being made to a standard color, accurate amounts of fluids and dispersions must be added, often in vex), small amounts. The slightest deviation from the formula results in off-color paint. Therefore, accurate delivery equipment is required.
Another example is where ingredients are added to achieve a material within a specific tolerance range of pH and/or viscosity limits. Again, precise control of additions in small quantities is essential, particularly for materials which are sensitive to fluctuations in pH or viscosity.
A typical apparatus which was used for precision pumping of fluids is shown in Cocks, U.S. Pat. No. 4,026,439, issued May 31, 1977 which uses a pneumatic control system. However, this control system does not control the pump accurately. Also, the disclosed liquid-activated check valves do not accurately control flow due to the failure of the valve seat to seal reliably when used with suspended pigmented solutions.
Falcoff, U.S. Pat. No. 4,494,677, issued Jan. 22, 1985 discloses an apparatus which uses a computer controlled pump to deliver fluid from a supply vessel to a mixing vessel. This disclosure does not allow for easy addition of materials to an on-line system, particularly for small amounts needed for fine adjustments of a formulation in manufacture.
An object of this invention is to allow easy and precise addition of materials to a process vessel or process system. Another object is to enable all fluids which are metered to the system are actually injected into the process vessel or stream, with no material left within the injection device.
Yet another object of the invention is to eliminate dead or empty space within the system through a recirculation mode to achieve air-free injection of variable quantities of a liquid. Once the system is filled with materials to be added, the recirculation mode may be used to resuspend materials within the fluid, such as pigments, and prevent inhomogeneity among the constituents.
Another objective of the invention is to have recirculation within the pumping systems, the injection valve and recirculation line back to a supply vessel while the piping and valving are directly connected the process line.